The Food and Drug Administration (FDA) has issued guidance for health care providers to contact patients who are currently taking unapproved animal-derived thyroid medications. The agency is advising that these patients be transitioned to FDA-approved synthetic thyroid hormone replacement medications.
According to the FDA, appropriate dosing of thyroid hormone replacement medication is important, as incorrect dosages can either cause side effects or reduce effectiveness. Synthetic thyroid medications approved by the FDA contain levothyroxine, liothyronine, or a combination of both. In contrast, animal-derived products—also known as desiccated thyroid extract—may have inconsistent dosages and may contain impurities.
The FDA emphasized its position in a statement: "Food and Drug Administration (FDA) is instructing health care providers to contact patients taking unapproved thyroid medications and help transition them to FDA-approved medications. Thyroid hormone replacement medications require administering the appropriate dosage based on the patient’s thyroid hormone levels, as a dose that is too high can cause side effects, and a dose that is too low will not be as effective. Synthetic (laboratory-made) thyroid hormone replacement medications, which are FDA approved, contain only levothyroxine or liothyronine, or a combination of these two. Animal-derived thyroid medications, also called desiccated thyroid extract, have a higher risk of containing inconsistent dosages or having other impurities."
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